When an engine is in a warm state, a ratio of air and fuel in the economy is in a range of 13:1-15:1 set by the factory. But when the engine starts in a cold state, the ratio of air and fuel needs to be in a higher range of 6:1-12:1 because the carburetor needs to provide additional fuel to the engine to ensure that the engine can start normally.
At present, a choke device is widely used to reduce the amount of air to achieve a high air-fuel ratio. An engine starting method usually includes the following steps: step (1), squeezing the purge bulb; step (2), closing the choke; step (3), opening the throttle fully or setting the throttle in the fast idle speed position; step (4), pulling an engine starter until a POP sound is generated; step (5), pulling the choke to a one-half open position; step (6), pulling the engine starter to start the engine; step (7), keeping the engine running warm; step (8), pulling the choke to a full open position; and step (9), increasing and decreasing the throttle to normal running. The disadvantages of the present choke device are as follows: firstly, steps are cumbersome; secondly, it is difficult to judge the POP sound, resulting in difficulty starting the engine; and thirdly, the engine is difficult to or cannot start at low temperature (such as 0 degree centigrade).